Experimental manipulations of nutrients and trophic structure across ecosystems

Nutrient availability, herbivore grazing pressure, and the indirect effects of top predators control the standing biomass, nutrient content and species diversity of primary producers to varying degrees across global ecosystems. For this comprehensive database, we systematically gathered data from the literature that experimentally manipulated (1) nutrients through fertilization, (2) herbivore pressure through exclusion, enclosion, or removal experiments, (3) predators through similar means, or (4) a combination of these treatment combinations. Special priority was given to studies that factorially manipulated multiple nutrients (especially N & P) or manipulated both nutrients and herbivores (bottom-up and top-down), and which measured species richness, biomass or nutrient content of autotrophic responses at the community level. In addition, the Trophic Cascades database (owned by E. Borer et al.) has been folded into this framework, as well as data from several other published analyses from restricted systems (e.g., H. Hillebrand periphyton database). The goals were manifold; however, the central objective was to compare with meta-analyses the relative effects of these experimental manipulations across global organismal functional groups and ecosystem types. To this end, the database was designed to be general and flexible in order to accomodate varying research questions, methodologies, spatial and temporal scales, and abiotic and biotic covariates reported across different studies. As of this writing (14 November 2006), the database contains nearly 2000 studies across terrestrial, freshwater and marine systems, and well over 10,000 treatment responses. Data are entered into four different tables in a relational design (study-level data, treatment/responses, local biotic covariates of response and manipulated taxa, & general/global taxonomic and functional characteristics of these taxa).

全球各类生态系统中，养分有效性、草食动物牧食压力以及顶级捕食者的间接效应，会在不同程度上调控初级生产者（primary producers）的现存生物量、养分含量与物种多样性。针对本综合数据库，我们系统收集了来自已发表文献的数据，这些文献通过实验开展了四类操控处理：(1) 施肥操控养分水平，(2) 通过移除、围封或去除实验操控草食动物压力，(3) 采用类似方法操控捕食者种群，或(4) 上述处理的组合干预。我们特别优先纳入那些采用析因设计操控多种养分（尤其是氮[N]与磷[P]），或同时操控养分与草食动物（即上行调控[bottom-up]与下行调控[top-down]）的研究，且这些研究均在群落层面测定了自养生物的物种丰富度、生物量或养分含量响应。此外，由E·博勒（E. Borer）等人维护的营养级联（Trophic Cascades）数据库，以及来自若干受限生态系统已发表分析的数据集（例如H·希勒布兰德[H. Hillebrand]的周丛生物[periphyton]数据库）均已整合至本数据库框架中。本数据库的研究目标较为多元，但核心目标是通过元分析（meta-analysis）对比各类实验操控在全球生物功能群与生态系统类型中的相对效应。为此，本数据库被设计为通用且灵活的框架，以适配不同研究中所报道的多样化研究问题、研究方法、时空尺度以及非生物与生物协变量。截至本撰写完成之时（2006年11月14日），本数据库涵盖了陆地、淡水与海洋生态系统中的近2000项研究，以及超过10000条处理响应数据。该数据库采用关系型数据库设计（relational design），数据存储于四张数据表中：研究层级数据、处理/响应数据、响应的本地生物协变量与操控类群数据，以及这些类群的通用/全球分类学与功能特征数据。